Oscillator devices and methods of operating such oscillator devices are disclosed. The oscillator devices include a current source, and an oscillation module to provide a clock signal. The frequency of the clock signal depends on the relationship between a threshold voltage of a transistor at the oscillation module and the current level provided by the current source. The transistor at the oscillation module is matched to a transistor at the current source so that the frequency of the clock signal is relatively insensitive to changes in device temperature.